There has long been a need in the field of drug delivery devices to have a drug released in the human or animal tissue at the place where it is most therapeutically effective and to have said drug released in the tissue in a controlled manner over a long period of time.
U.S. Pat. Nos. 4,093,709 and 4,304,767 disclose polymers which can be used as a matrix to contain a drug. The polymers contain labile backbone bonds which hydrolyze in the presence of water causing a controlled erosion of the matrix and resultant release of the drug. These polymers have the disadvantage, however, that they hydrolyze extremely slowly.
The polymers of the instant invention have the advantage that the pendant acid functionalities catalyze the hydrolysis of the labile polymer backbone bonds.